I went from the 12k's to Ushio 10k's first. Pretty intense bulbs with a good reputation for longer life. I know there will be those who will claim differently, but I just couldn't get past the "yellow" they always seemed to look like "to me". I used them for about 10 months, got pretty decent SPS growth out of them, and then decided to move on.
I wanted to try something more towards the blue end of things, but still get good PAR numbers. I was really tempted by the Aquaconnects, but just couldn't get myself to cough up the hundred plus dollars per bulb. After doing a lot of reading amongst the SPS forum threads and gathering up info on who was running what, I decided to go with the Reeflux 10k's. I'm pretty happy with them. I have continued to get good growth, but have more of the white light that I want with much less yellow. It is funny that the glow I get in the room is that pink color they seem to be known for, but looking at my tank I really don't notice it. I run them with VHO actinics. Much cheaper bulb with good numbers. Kinda wish I had more room to squeeze another bulb in over the tank 'cause I'd probably put a 20k up there somewhere to get more blue, but oh well. At any rate, so far so good with these. Corals have pretty good color under them.